This is by far the best FF add-on I have, and it was just added a few hours ago. Nothing online is as important as being able to comfortably read and view images when browsing. If your eyes get hurt/strained it not only impacts your browsing experience but it can mess with your eye health long term. This add-on is allowing me to surf at night with minimal to no room lighting and not be blinded when a normally overly white page loads. I have just begun to play with the wide range of customizable options available. I am feeling a donation is heading to a dev after I play with this a little more and learn how to best use it.